In this newsletter we discuss “transgenerational epigenetic inheritance” – the idea that a behavioural response can be transmitted from one generation to the next. Evidence that this could happen with a phenomenon called “learned avoidance” in C. elegans was first reported in 2019, only to be disputed last year. Now a third group has observed this phenomenon – in which C. elegans learns to avoid pathogenic bacteria – can be transmitted for two generations. Plus, the evolution of complementary sex determination, and targeting aphids with green pesticides.
– Peter Rodgers, Chief Magazine Editor, eLife
Researchers are developing green pesticides to target aphids. Image credit: Viktor Forgacs (CC0)
Since its introduction in 1921, the BCG vaccine – which is primarily used against tuberculosis – has saved many more lives than can be explained by it protecting people against TB alone. The mechanism behind this mystery remained elusive until 2012, almost a century later, when it was discovered that the cells of the innate immune system possess a form of memory that allows them to be “trained”. For decades, it had been known that adaptive immune cells have a memory function, but it was assumed that innate immune cells did not. This editorial introduces a collection of articles that discuss progress towards a better understanding of memory in the innate immune system, and efforts to develop new vaccines and therapeutics based on trained immunity.
The worm C. elegans can learn to avoid a pathogenic bacterium called P. aeruginosa. In 2019, researchers at Princeton University observed that this “learned avoidance” could be transmitted for up to four generations, thus allowing worms that have never encountered P. aeruginosa to benefit from the experiences of previous generations. Recently, however, a group at Harvard University observed the transmission of learned avoidance to a first generation, but not to a second generation. Now, as detailed in this Insight article, a third group (at Illinois State University) has observed learned avoidance in both the first and second generations. Differences in the methods used to immobilize the worms during the experiments seem to explain why the Princeton and Illinois State groups observed learned avoidance in the second generation, and the Harvard group did not.
The peach aphid is a parasitize that attacks crops and spreads various plant viruses. Peach aphids can be controlled with chemical pesticides, but concerns about environmental pollution and pesticide resistance are driving efforts to develop new, environmentally friendly insecticides. Some of these efforts have focused on betulin, a metabolite produced by peaches that is highly toxic to aphids. An important step in developing a green pesticide based on betulin is to understand why it is toxic in aphids. Now, as described in a paper published in eLife, researchers have shown that betulin targets a receptor protein in the nervous system of the aphids. It does this by inhibiting the expression of the gene for the receptor, and also by binding to the receptor itself.
In most animals sex is determined by sex chromosomes. However, about 12% of animal species are haplodiploid – with females having twice as many chromosomes as males – and these species must rely on other strategies for sex determination. In "complementary sex determination" (CSD), for example, having different alleles at a sex determination locus triggers female development, whereas having identical alleles (or just one allele) at this locus leads to male development. Loci for CSD have been mapped in honeybees and two ant species, but little is known about their evolutionary history. Now, as reported in eLife, researchers have identified a CSD locus in a species of ant called Ooceraea biroi that is similar to the CSD loci found in other ant species, but distinct from the locus in honeybees. This implies that this mechanism for sex determination has been conserved since it evolved in a common ancestor around 112 million years ago.
Researchers recently discovered a protein called RNF213 that is able to detect an unusually wide range of pathogens when they enter our cells. RNF213 tags any pathogens it detects with a small protein called ubiquitin, marking them for destruction by the immune system. However, some pathogens – such as Shigella, a bacterium that kills hundreds of thousands of people every year – can avoid the attentions of RNF213. Now, as explained in the Insight article, Shigella performs this escape act by turning the tables and tagging RNF213 with ubiquitin. Other bacteria also target RNF213, so it could be a potential target for new drugs that can fight bacterial infections.
Academia should resume control of scientific publishing using non-profit publishing models, and incentive systems should be changed to reward quality, not quantity, according to an article based on a meeting organized by the Royal Swedish Academy of Sciences earlier this year. The “Stockholm Declaration” also calls for new mechanisms to prevent and detect fake publications from paper mills, and new legislation and policies to increase publishing quality and protect the integrity of science.
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